1950s 1951 Cadillac Oil Pump

[Davidcamper]

Does anyone know why the new oil pump rebuild kit has straight gears versus at an angle on the original? Does it effect the amount of oil pumped?

[Jay Friedman]

I don't know why the kit has straight gears versus gears at an angle (helical gears?) on the original, nor whether this affects the amount of oil pumped.  If you have doubts, just use the old gears, as they don't normally wear out. 

A word of caution.  My experience with oil pump repair kits for Cadillac 331 motors is that the spring for the oil pressure relief valve supplied in these kits is usually much stiffer than the original spring.  When installed these stiffer springs don't allow the relief valve to sufficiently open.  The result is that when the motor is put back together and started, the oil pressure will be much too high.  331 oil pressure should be at 30-35 psi at road speeds, but will be 60 or 70 psi with the stiffer springs, which is undesirable.  I suggest you use the original spring, since in my experience they don't wear out. This once happened to my own '49's 331, and I had to take everything apart a second time to put back the original spring.

Another good thing to do is to check the smoothness of the inside of the bottom plate of the oil pump.  If it is rough because of the rotation of the gears, you can smooth it out with a file or sandpaper. 

[Poncholover]

Straight gears are cheaper. Give the customer what they want!

[Davidcamper]

Jay, thank you for sharing your experience and your advice. I will follow it.
Shalom